Engineered kidneys: principles, progress, and prospects

There is an urgent need for new ways to treat end-stage renal disease: by promoting regeneration in situ, by repopulating decellularized donor organs with a patient's own stem cells, or by making entirely new kidneys. There are two broad strategies for making new kidneys: precision engineering by positioning everything exactly – for example, by 3D printing – or supporting cells’ self-organizing ability. We describe the latter approach, which begins with a suspension of renogenic stem cells and produces a small kidney with nephrons, a collecting duct system, active transport, and an ability to integrate with host vasculature. Many problems have to be solved before these kidneys are directly clinically useful, including size, maturation, provision of a ureter, and production from human-induced pluripotent stem cells. Even the existing engineered kidneys, if they can be made from human rather than animal cells, may be useful for assays for adverse drug reactions that will be free of the problems of extrapolating from animal tests to predicted human responses.